Plate heat exchanger

ABSTRACT

A plate heat exchanger is disclosed. The plate heat exchanger of the present disclosure includes: a first plate having a wavy first heat transfer surface through which a first fluid flows; a second plate having a wavy second heat transfer surface through which a second fluid flows, the first plate and the second plate being stacked on top of each other; and ribs provided at a portion of the first heat transfer surface, wherein the wavy first heat transfer surface has alternating ridges and grooves; and the ribs project from the grooves toward the ridges in the first heat transfer surface, to come into contact with the second plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Korean Patent Application No. 10-2020-0027924, filed on Mar. 5, 2020 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a plate heat exchanger, and more particularly to a plate heat exchanger in which heat transfer performance may be improved by reducing a flow cross-sectional area of a refrigerant.

2. Description of the Related Art

Generally, an air conditioner is a device for heating or cooling an indoor space by compression, condensation, expansion and evaporation of a refrigerant. For heating the indoor space, an indoor heat exchanger, provided for an indoor unit, functions as a condenser through which high-temperature and high-pressure refrigerant passes through; and an outdoor heat exchanger, provided for an outdoor unit, functions as an evaporator through which low-temperature and low-pressure refrigerant passes through. By contrast, for cooling the indoor space, the indoor heat exchanger functions as an evaporator, and the outdoor heat exchanger functions as a condenser.

Such heat exchanger may be provided as a plate heat exchanger, thereby allowing effective heat transfer between different fluids (i.e., water and refrigerant). For example, KR10-2008-0006122 (Jan. 16, 2008) discloses a plate type heat exchanger which provides effective heat exchange in a flow passage formed between a plurality of heat transfer plates.

Accordingly, there is a need for research and development to improve heat transfer performance effectively by adjusting a flow cross-sectional area of fluids flowing through the plate heat exchanger.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to solve the above and other problems.

It is another object of the present disclosure to provide a plate heat exchanger, in which heat transfer performance may be improved by reducing a flow cross-sectional area of a refrigerant.

It is yet another object of the present disclosure to provide a plate heat exchanger, in which the plate has ribs to block or guide a flow of a refrigerant.

It is still another object of the present disclosure to provide a plate heat exchanger, in which the plate has a wavy shape and is provided with ribs, such that the manufacturing process may be simplified.

In accordance with an aspect of the present disclosure, the above and other objects can be accomplished by providing a plate heat exchanger, including: a first plate having a wavy first heat transfer surface through which a first fluid flows; a second plate having a wavy second heat transfer surface through which a second fluid flows, the first plate and the second plate being stacked on top of each other; and ribs provided at a portion of the first heat transfer surface, wherein the wavy first heat transfer surface has alternating ridges and grooves; and the ribs project from the grooves toward the ridges in the first heat transfer surface, to come into contact with the second plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a plate heat exchanger according to an embodiment of the present disclosure.

FIG. 2 is a front view of a first plate according to an embodiment of the present disclosure.

FIG. 3 is an enlarged view of ribs provided on a first plate according to an embodiment of the present disclosure.

FIG. 4 is a rear view of FIG. 3.

FIG. 5 is a graph explaining an increase in heat exchange efficiency of a plate heat exchanger according to an embodiment of the present disclosure.

FIGS. 6 to 9 are diagrams illustrating various examples of shapes and arrangements of ribs according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to give any special meaning or function.

It will be noted that a detailed description of known arts will be omitted if it is determined that the detailed description of the known arts can obscure the embodiments of the disclosure. Further, the accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings.

The terms ‘first’, ‘second’, etc. may be used to describe various components, but the components are not limited by such terms. The terms are used only for the purpose of distinguishing one component from other components.

When an arbitrary component is described as “being connected to” or “being coupled to” another component, this should be understood to mean that still another component(s) may exist between them, although the arbitrary component may be directly connected to or directly coupled to another component. In contrast, when an arbitrary component is described as “being directly connected to” or “being directly coupled to” another component, this should be understood to mean that no component exists between them.

A singular expression can include a plural expression as long as it does not have an apparently different meaning in context.

In the following description, although described with reference to certain drawings, reference numerals not shown in the drawings may be referred to if necessary, and the reference numerals not shown in the drawings are used when they are shown in the other figures.

Referring to FIG. 1, the plate heat exchanger 1 includes a plurality of plates 10 and 20 which are stacked on top of each other.

In the plate heat exchanger 1, a direction in which the plurality of plates 10 and 20 are stacked on top of each other may be referred to as a front-rear direction FR. Further, the plurality of plates 10 and 20 may be elongated in an up-down direction UD. A left-right direction LR may be a direction perpendicular to the up-down direction UD. In addition, for convenience of explanation, FIG. 1 illustrates an example in which the plate heat exchanger 1 has a greater length in the up-down direction UD than in the left-right direction LR, but the length of the plate heat exchanger 1 in the up-down direction UD may also be approximately equal to or shorter than the length in the left-right direction LR. Further, FIG. 1 illustrates an example in which the plate heat exchanger 1 includes three plates 10 and 20, but the number of the plates 10 and 20 are not limited thereto.

A first end plate 50 may cover a front portion of a plate disposed at a foremost position among the plurality of plates 10 and 20. In this case, a flow passage, through which fluids flow, may be formed between the first end plate 50 and the foremost plate. A second end plate 30 may cover a rear portion of a plate disposed at a rearmost position among the plurality of plates 10 and 20. In this case, a flow passage, through which fluids flow, may be formed between the second end plate 30 and the rearmost plate. Further, the fluids may be blocked from flowing rearward from the second end plate 30.

A front cover 60 may be coupled to the first end plate 50 to cover a front portion of the first end plate 50. A rear cover 40 may be coupled to the second end plate 30 to cover a rear portion of the second end plate 50.

Each of the front cover 60, the first end plate 50, and the plurality of plates 10 and 20 may be provided with a port, through which a first fluid R or a second fluid W is introduced or discharged. Here, the port may be referred to as a hole.

For example, a second fluid W may be introduced through an inflow port 61 of the front cover 60, to flow through a first flow passage connecting an inflow port 51 of the first end plate 50 and inflow ports 11 and 21 of the plurality of plates 10 and 20. Further, a portion of the second fluid W, flowing through the first flow passage, may flow downward along a heat transfer surface (not numbered) of some of the plurality of plates 10 and 20. In addition, the second fluid W, flowing through the first flow passage and/or the heat transfer surface, may be joined in a second flow passage to be discharged to the outside through a discharge port 62 of the front cover 60. Here, the second flow passage may connect discharge ports 12 and 22 of the plurality of plates 10 and 20 and a discharge port 52 of the first end plate 50. In this case, the second fluid W may be water.

For example, a first fluid R may be introduced through an inflow port 63 of the front cover 60, to flow through a third flow passage connecting an inflow port 53 of the first end plate 50 and inflow ports 13 and 23 of the plurality of plates 10 and 20. Further, a portion of the first fluid R, flowing through the third flow passage, may flow upward along a heat transfer surface (not numbered) of some of the plurality of plates 10 and 20. In addition, the first fluid R, flowing through the third flow passage and/or the heat transfer surface, may be joined in a fourth flow passage to be discharged to the outside through a discharge port 64 of the front cover 60. Here, the fourth flow passage may connect discharge ports 14 and 24 of the plurality of plates 10 and 20 and a discharge port 54 of the first end plate 50. In this case, the first fluid R may be R410A or R32.

Referring to FIGS. 1 and 2, the plurality of plates 10 and 20 may include the first plate 10 and the second plate 20 which are stacked on top of each other in the front-rear direction FR. In this case, the first plate 10 may have a first heat transfer surface 110 through which the first fluid R flows. Further, the second plate 20 may have a second heat transfer surface 210 through which the second fluid W flows.

The first heat transfer surface 110 of the first plate 10 may have a wave shape with alternating ridges 111 and grooves 112. For example, the wave shape of the first heat transfer surface 110 may be a shape of the letter V of the alphabet or inverted-V shape. Such shape of the first heat transfer surface 110 may be referred to as a chevron. Further, the above description of the first plate 10 may also apply to the second plate 20.

Accordingly, a heat transfer area of the first fluid R, flowing over the first heat transfer surface 110, and a heat transfer area of the second fluid W flowing over the second heat transfer surface 210 may be increased, thereby improving heat transfer performance therebetween.

For example, the first plate 10 and the second plate 20 may be made of a metal material having excellent thermal conductivity and pressure resistance. For example, the first plate 10 and the second plate 20 may be made of a stainless material.

Referring to FIGS. 2 and 3, the plate heat exchanger 1 may include ribs 120 provided on a portion of the first heat transfer surface 110. In this case, the ribs 120 may project from the grooves 112 of the first heat transfer surface 110 toward the ridges 111, to come into contact with the adjacent second plate 20.

Accordingly, the ribs 120 may block the flow of the first fluid R over the first heat transfer surface 110, such that a flow cross-sectional area of the first fluid R may be reduced and a flow velocity of the first fluid R may be increased. That is, in consideration of thermal convection properties, heat transfer performance between the first fluid R and the second fluid W may be improved according to the increase in flow velocity of the first fluid R. The ribs 120 may guide the flow of the first fluid R over the first heat transfer surface 110.

Referring to FIGS. 3 and 4, the ribs 120 may be pressed on the plate 10 to be formed together with the ridges 111. That is, the first plate 10 has the ribs 120 along with the first heat transfer surface 110 having a wave shape, such that the manufacturing process may be simplified.

In this case, the ribs 120 project forward from a front surface of the first plate 10 and are recessed forward from a rear surface of the first plate 10, such that a flow cross-sectional area of the second fluid W, flowing over the second plate 20, may be maintained regardless of the presence of the ribs 120.

Referring to FIG. 5, an optimum point of heat exchange efficiency according to an increase in water flow velocity may be different from an optimum point of heat exchange efficiency according to an increase in refrigerant flow velocity.

That is, as a flow cross-sectional area of a fluid is reduced, a flow velocity of the fluid increases, such that a convective heat transfer coefficient increases. In this case, however, pressure loss of the fluid increases, requiring a trade-off between the convective heat transfer coefficient and the pressure loss of the fluid in terms of heat exchange efficiency. Further, such properties may vary depending on the types of fluids.

As shown in the graph, the optimum point of heat exchange efficiency according to the increase in refrigerant flow velocity is relatively higher than the optimum point of heat exchange efficiency according to the increase in water flow velocity. Accordingly, it is preferred to reduce a flow cross-sectional area of the first fluid R corresponding to a refrigerant by using the ribs 120 provided on the first heat transfer surface 110, thereby increasing the flow velocity and heat exchange efficiency.

Referring to FIG. 6, the first heat transfer surface 110 may be elongated in the up-down direction UD, and the ridges 111 and the grooves 112 may be elongated in a direction intersecting the up-down direction UD. Further, the first heat transfer surface 110 may be formed to be symmetric in the left-right direction LR with respect to a virtual boundary Bo extending in the up-down direction UD. That is, the wave shape of the first heat transfer surface 110 may be bilaterally symmetric about the boundary Bo.

The ribs 120 may include a plurality of ribs 121, 122, and 123 which are spaced apart from each other in the up-down direction UD. That plurality of ribs 121, 122, and 123 may include a first rib 121, a second rib 122, and a third rib 123. However, the number of the ribs 121, 122, and 123 are not limited thereto.

The first rib 121 may be adjacent to a right edge Er of the first heat transfer surface 110. The first rib 121 may be elongated in the left-right direction LR. One end of the first rib 121 may be disposed on the right edge Er of the first heat transfer surface 110, and the other end thereof may be disposed on the boundary Bo.

The second rib 122 may be adjacent to a left edge El of the first heat transfer surface 110. The second rib 122 may be elongated in the left-right direction LR. One end of the second rib 122 may be disposed on the left edge El of the first heat transfer surface 110, and the other end thereof may be disposed on the boundary Bo.

The third rib 123 may be adjacent to the right edge Er of the first heat transfer surface 110. The third rib 123 may be elongated in the left-right direction LR. One end of the third rib 122 may be disposed on the right edge Er of the first heat transfer surface 110, and the other end thereof may be disposed on the boundary Bo.

Accordingly, the flow R1 of the first fluid R over the first heat transfer surface 110 may continue from the inflow port 13 to the discharge port 14 while bypassing the first rib 121, the second rib 122, and the third rib 123.

Referring to FIG. 7, the first rib 121′, the second rib 122′, and the third rib 123′ are elongated in the left-right direction LR, and may be spaced apart from the edges of the first heat transfer surface 110.

One end of the first rib 121′ may be spaced apart from the right edge Er of the first heat transfer surface 110 by a first distance d1, and the other end thereof may be disposed on the boundary Bo. One end of the second rib 122′ may be spaced apart from the left edge El of the first heat transfer surface 110 by a second distance d2, and the other end thereof may be disposed on the boundary Bo. One end of the third rib 123′ may be spaced apart from the right edge Er of the first heat transfer surface 110 by a third distance d3, and the other end thereof may be disposed on the boundary Bo. For example, the first distance d1, the second distance d2, and the third distance d3 may be equal to each other.

Accordingly, a flow R2 of the first fluid R over the first heat transfer surface 110 may continue from the inflow port 13 to the discharge port 14 while bypassing the first rib 121′, the second rib 122′, and the third rib 123′.

In this case, the flow R2 of the first fluid R may be divided into a first flow R21 and a second flow R22. Here, the first flow R21 may be formed across the boundary bo. Further, the second flow R22 may be formed between one end of each of the first rib 121′, the second rib 122′, and the third rib 123′ and the edge of the first heat transfer surface 110 which is adjacent to the one end. That is, the second flow R22, formed along the edge of the first heat transfer surface 110, may prevent the formation of a vortex in the flow R2 of the first fluid R, thereby preventing stagnation of the fluid flow.

Referring to FIG. 8, the first rib 121″ may include a plurality of first ribs 121″, each of which is elongated in the left-right direction LR and which are spaced apart from each other in the left-right direction LR. The second rib 122″ may include a plurality of second ribs 122″, each of which is elongated in the left-right direction LR and which are spaced apart from each other in the left-right direction LR. The third rib 123″ may include a plurality of third ribs 123″, each of which is elongated in the left-right direction LR and which are spaced apart from each other in the left-right direction LR.

The plurality of first ribs 121″ may be spaced apart from each other by a fourth distance d4 including the right edge Er of the first heat transfer surface 110. The plurality of second ribs 122″ may be spaced apart from each other by a fifth distance d5 including the left edge El of the first heat transfer surface 110. The plurality of third ribs 123″ may be spaced apart from each other by a sixth distance d6 including the right edge Er of the first heat transfer surface 110. For example, the fourth distance d4, the fifth distance d5, and the sixth distance d6 may be equal to each other.

Accordingly, a flow R3 of the first fluid R on the first heat transfer surface 110 may continue from the inflow port 13 to the discharge port 14 while bypassing the plurality of first ribs 121″, the plurality of second ribs 122″, and the plurality of third ribs 123″.

In this case, the flow R3 of the first fluid R may be divided into a first flow R31, a second flow R32, and a third flow R33. Here, the first flow R31 may be formed across the boundary bo. Further, the second flow R32 may be formed between one end of each of the first rib 121″, the second rib 122″, and the third rib 123″ and the edge of the first heat transfer surface 110 which is adjacent to the one end. In addition, the third flow R33 may be formed between the plurality of first ribs 121″, the plurality of second ribs 122″, and the plurality of third ribs 123″. That is, the second flow R32, formed along the edge of the first heat transfer surface 110, may prevent the formation of a vortex in the flow R3 of the first fluid R; and the third flow R33, formed between the adjacent ribs, may cause turbulence in the flow R3 of the first fluid R, thereby improving heat transfer performance of the second fluid W.

Referring to FIG. 9, the first rib 121′″ may include a plurality of first ribs 121′″, each of which is elongated in a direction intersecting the left-right direction LR and which are spaced apart from each other in the left-right direction LR. The second rib 122′″ may include a plurality of second ribs 122′″, each of which is elongated in a direction intersecting the left-right direction LR and which are spaced apart from each other in the left-right direction LR. The third rib 123′″ may include a plurality of third ribs 123′″, each of which is elongated in a direction intersecting the left-right direction LR and which are spaced apart from each other in the left-right direction LR.

Each of the plurality of first ribs 121′″ may form a first angle theta 1 with a virtual line extending rightward from the boundary Bo. Here, the first angle theta 1 may be an acute angle. Each of the plurality of second ribs 122′″ may form a second angle theta 2 with a virtual line extending leftward from the boundary Bo. Here, the second angle theta 2 may be an acute angle. Each of the plurality of third ribs 123′″ may form a third angle theta 3 with a virtual line extending rightward from the boundary Bo. Here, the third angle theta 3 may be an acute angle.

The plurality of first ribs 121′″ may be spaced apart from each other by a seventh distance d7 including the right edge Er of the first heat transfer surface 110. The plurality of second ribs 122′″ may be spaced apart from each other by an eighth distance d8 including the left edge El of the first heat transfer surface 110. The plurality of third ribs 123′″ may be spaced apart from each other by a ninth distance d9 including the right edge Er of the first heat transfer surface 110. For example, the seventh distance d7, the eighth distance d8, and the ninth distance d9 may be equal to each other.

Accordingly, a flow R4 of the first fluid R on the first heat transfer surface 110 may continue from the inflow port 13 to the discharge port 14 while bypassing the plurality of first ribs 121′″, the plurality of second ribs 122′″, and the plurality of third ribs 123′″.

In this case, the flow R4 of the first fluid R may be divided into a first flow R41, a second flow R42, and a third flow R43. Here, the first flow R41 may be formed across the boundary bo. Further, the second flow R42 may be formed between one end of each of the first rib 121′″, the second rib 122′″, and the third rib 123′″ and the edge of the first heat transfer surface 110 which is adjacent to the one end. In addition, the third flow R43 may be formed between the plurality of first ribs 121″, the plurality of second ribs 122′″, and the plurality of third ribs 123″. That is, the second flow R42, formed along the edge of the first heat transfer surface 110, may prevent the formation of a vortex in the flow R4 of the first fluid R; and the third flow R43, formed between the adjacent ribs, may cause turbulence in the flow R4 of the first fluid R, thereby improving heat transfer performance of the second fluid W.

Particularly, the plurality of first ribs 121′″, the plurality of second ribs 122″, and the plurality of third ribs 123″ are inclined, thereby effectively preventing the formation of the vortex and promoting turbulence in the fluid flows.

In accordance with an aspect of the present disclosure, provided is a plate heat exchanger including: a first plate having a wavy first heat transfer surface through which a first fluid flows; a second plate having a wavy second heat transfer surface through which a second fluid flows, the first plate and the second plate being stacked on top of each other; and ribs provided at a portion of the first heat transfer surface, wherein the wavy first heat transfer surface has alternating ridges and grooves, and the ribs project from the grooves toward the ridges in the first heat transfer surface, to come into contact with the second plate.

In accordance with another aspect of the present disclosure, the ribs may be pressed on the first plate to be formed together with the ridges.

In accordance with another aspect of the present disclosure, the first heat transfer surface may be elongated in an up-down direction; the ridges and the grooves of the first heat transfer surface may be elongated in a direction intersecting the up-down direction; and the ribs may further include a plurality of ribs which are spaced apart from each other in the up-down direction.

In accordance with another aspect of the present disclosure, the plurality of ribs may further include a first rib adjacent to a right edge of the first heat transfer surface; a second rib adjacent to a left edge of the first heat transfer surface and disposed above the first rib; and a third rib adjacent to the right edge of the first heat transfer surface and disposed above the second rib.

In accordance with another aspect of the present disclosure, each of the first rib, the second rib, and the third rib may be elongated in a left-right direction.

In accordance with another aspect of the present disclosure, the first heat transfer surface may be symmetric in the left-right direction with respect to a virtual boundary extending in the up-down direction, wherein one end of the first rib may be disposed on the right edge of the first heat transfer surface, and the other end thereof may be disposed on the boundary; one end of the second rib may be disposed on the left edge of the first heat transfer surface, and the other end thereof may be disposed on the boundary; and one end of the third rib may be disposed on the right edge of the first heat transfer surface, and the other end thereof may be disposed on the boundary.

In accordance with another aspect of the present disclosure, the first heat transfer surface may be symmetric in the left-right direction with respect to a virtual boundary extending in the up-down direction, wherein one end of the first rib may be spaced apart from the right edge of the first heat transfer surface by a first distance, and the other end thereof may be disposed on the boundary; one end of the second rib may be spaced apart from the left edge of the first heat transfer surface by a second distance, and the other end thereof may be disposed on the boundary; and one end of the third rib may be spaced apart from the right edge of the first heat transfer surface by a third distance, and the other end thereof may be disposed on the boundary.

In accordance with another aspect of the present disclosure, the first distance, the second distance, and the third distance may be equal to each other.

In accordance with another aspect of the present disclosure, the first rib may further include a plurality of first ribs which are spaced apart from each other in the left-right direction; the second rib may further include a plurality of second ribs which are spaced apart from each other in the left-right direction; and the third rib may further include a plurality of third ribs which are spaced apart from each other in the left-right direction.

In accordance with another aspect of the present disclosure, the plurality of first ribs may be spaced apart from each other by a fourth distance including the right edge of the first heat transfer surface; the plurality of second ribs may be spaced apart from each other by a fifth distance including the left edge of the first heat transfer surface; and the plurality of third ribs may be spaced apart from each other by a sixth distance including the right edge of the first heat transfer surface.

In accordance with another aspect of the present disclosure, the plurality of first ribs, the plurality of second ribs, and the plurality of third ribs may be elongated in the left-right direction.

In accordance with another aspect of the present disclosure, the plurality of first ribs, the plurality of second ribs, and the plurality of third ribs may be elongated in a direction intersecting the left-right direction.

In accordance with another aspect of the present disclosure, the first fluid may be a refrigerant, and the second fluid may be water.

The effects of the plate heat exchanger according to the present disclosure will be described.

Firstly, according to at least one of the embodiments of the present disclosure, there is provided a plate heat exchanger in which heat transfer performance may be improved by reducing a flow cross-sectional area of a refrigerant.

Secondly, according to at least one of the embodiments of the present disclosure, there is provided a plate heat exchanger, in which the plate has ribs to block or guide a flow of a refrigerant.

Thirdly, according to at least one of the embodiments of the present disclosure, there is provided a plate heat exchanger, in which the plate has a wavy shape and is provided with ribs, such that the manufacturing process may be simplified.

Certain embodiments or other embodiments of the disclosure described above are not mutually exclusive or distinct from each other. Any or all elements of the embodiments of the disclosure described above may be combined or combined with each other in configuration or function.

For example, a configuration “A” described in one embodiment of the disclosure and the drawings and a configuration “B” described in another embodiment of the disclosure and the drawings may be combined with each other. Namely, although the combination between the configurations is not directly described, the combination is possible except in the case where it is described that the combination is impossible.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 

What is claimed is:
 1. A plate heat exchanger, comprising: a first plate having a wavy first heat transfer surface through which a first fluid flows; a second plate having a wavy second heat transfer surface through which a second fluid flows, the first plate and the second plate being stacked on top of each other; and ribs provided at a portion of the first heat transfer surface, wherein: the wavy first heat transfer surface has alternating ridges and grooves; and the ribs project from the grooves toward the ridges in the first heat transfer surface, to come into contact with the second plate.
 2. The plate heat exchanger of claim 1, wherein the ribs are pressed on the first plate to be formed together with the ridges.
 3. The plate heat exchanger of claim 1, wherein: the first heat transfer surface is elongated in an up-down direction; the ridges and the grooves of the first heat transfer surface are elongated in a direction intersecting the up-down direction; and the ribs further comprise a plurality of ribs which are spaced apart from each other in the up-down direction.
 4. The plate heat exchanger of claim 3, wherein the plurality of ribs further comprise: a first rib adjacent to a right edge of the first heat transfer surface; a second rib adjacent to a left edge of the first heat transfer surface and disposed above the first rib; and a third rib adjacent to the right edge of the first heat transfer surface and disposed above the second rib.
 5. The plate heat exchanger of claim 4, wherein each of the first rib, the second rib, and the third rib is elongated in a left-right direction.
 6. The plate heat exchanger of claim 5, wherein the first heat transfer surface is symmetric in the left-right direction with respect to a virtual boundary extending in the up-down direction, wherein: one end of the first rib is disposed on the right edge of the first heat transfer surface, and the other end thereof is disposed on the boundary; one end of the second rib is disposed on the left edge of the first heat transfer surface, and the other end thereof is disposed on the boundary; and one end of the third rib is disposed on the right edge of the first heat transfer surface, and the other end thereof is disposed on the boundary.
 7. The plate heat exchanger of claim 5, wherein the first heat transfer surface is symmetric in the left-right direction with respect to a virtual boundary extending in the up-down direction, wherein: one end of the first rib is spaced apart from the right edge of the first heat transfer surface by a first distance, and the other end thereof is disposed on the boundary; one end of the second rib is spaced apart from the left edge of the first heat transfer surface by a second distance, and the other end thereof is disposed on the boundary; and one end of the third rib is spaced apart from the right edge of the first heat transfer surface by a third distance, and the other end thereof is disposed on the boundary.
 8. The plate heat exchanger of claim 7, wherein the first distance, the second distance, and the third distance are equal to each other.
 9. The plate heat exchanger of claim 4, wherein: the first rib further comprises a plurality of first ribs which are spaced apart from each other in the left-right direction; the second rib further comprises a plurality of second ribs which are spaced apart from each other in the left-right direction; and the third rib further comprises a plurality of third ribs which are spaced apart from each other in the left-right direction.
 10. The plate heat exchanger of claim 9, wherein: the plurality of first ribs are spaced apart from each other by a fourth distance including the right edge of the first heat transfer surface; the plurality of second ribs are spaced apart from each other by a fifth distance including the left edge of the first heat transfer surface; and the plurality of third ribs are spaced apart from each other by a sixth distance including the right edge of the first heat transfer surface.
 11. The plate heat exchanger of claim 9, wherein the plurality of first ribs, the plurality of second ribs, and the plurality of third ribs are elongated in the left-right direction.
 12. The plate heat exchanger of claim 9, wherein the plurality of first ribs, the plurality of second ribs, and the plurality of third ribs are elongated in a direction intersecting the left-right direction.
 13. The plate heat exchanger of claim 9, wherein the first fluid is a refrigerant, and the second fluid is water. 